Apparatus for deep drawings containers of thermoplastic film material

ABSTRACT

An apparatus of forming containers of thermoplastic film material, said containers having back-cut portions, said apparatus comprising the means of maintaining the film material preheated into the plasticized range stressed over the opening of a mold means and of urging it into said mold means after a mechanical prestretching by a pneumatic pressurizing against the walls of said mold means until the solidification thereof, the margin of the molded article being severed to the desired dimension and said mold means divided in longitudinal direction being opened for the removal thereof, said apparatus being characterized by the fact that said mold means is opened only within the region having the back-cut portions and a region at least uninterrupted on its circumference being moved along the molded article toward a cutting plate for severing.

United States Patent 1191 Merklinghaus 1 1 Jan. 8, 1974 [54] APPARATUSFOR DEEP DRAWINGS 3,218,379 11/1965 Edwards 425/387 X CONTAINERS OFTHERMOPLASTIC FILM 3,342,914 /1967 Edwards 425/388 X 3,357,053 12/1967Lyon et a1... 425/292 MATERIAL 3,450,807 6/1969 Cheney 1. 425/388 x [75]Inventor; Horst Merknnghaus, 3,121,916 2/1964 Edwards 425/340HilchenbacbAnenbach, Germany 3,178,771 4/1965 Fischer 425/302 3,514,5095/1970 Hoffcr et al. 425/292 X [731 Assignees: Tedeco, N.V., Deventer,

Netherlands; Tedeco Verpackung Przmary Exammer-J. Howard Flint, Jr.Hamburg Germany Attorney-Robert M. Wolters [22] Filed: Aug. 16, 1972[21] Appl. No: 280,975 [57] ABSTRACT Rel ted US. A li ti D t Anapparatus of forming containers of thermoplastic [63] Continuation ofSer No 6] 361 5 1970 film material, said containers having back-cutporabandoned i tions, said apparatus comprising the means of maintainingthe film material preheated into the plasticized [30] ForeignApplication p Data range stressed over the opening of a mold means andAu 6 [969 German P 19 39 872 2 of urging it into said mold means after amechanical y prestretching by a pneumatic pressurizing against the wallsof said mold means until the solidification [52] US. Cl. 425/292,4zslzgigjilsc/pssv thereof the margin of the molded article being sew[51] Int Cl 1329c 3 ered to the desired dimension and said mold means{58] Fie'ld 292 310 divided in longitudinal direction being opened forthe 340 removal thereof, said apparatus being characterized by the factthat said mold means is opened only within [56] References cited thelregion having thedback-eut portionsf and a rggi on at east unlnterrupteon 1ts cz1rcum erence e1ng UNITED STATES PATENTS moved along the moldedarticle toward a cutting plate 3,259,942 7/1966 POiltlS 425/387 X forevering 3,465,071 9/1969 Edwards 425/397 X 3,510,913 5/1970 Edwards425/397 X 5 Claims, 2 Drawing Figures I APPARATUS FOR DEEP DRAWINGSCONTAINERS OF THERMOPLASTIC FILM MATERIAL This is a continuationapplication of Ser. No. 61,361, filed Aug. 5, 1970, which is nowabandoned.

This invention relates to an apparatus for deep drawing containers ofthermoplastic film material, said containers having back-cut portions.

Deep-drawn containers have found broad acceptance for packaging aplurality of substances and articles and in particular also for thepackaging of food. In many cases the shape of a downwardly convergingsteep truncated cone is selected for the containers, the upper rim ofwhich is formed into a flange to which a cover disc is connected bywelding after filling the container. This cover disc hermetically sealsthe container. Such containers are not very demanding regarding theapparatus formed for the manufacture thereof, and therefore they canreadily be made with simple tooling. It is a detrimental effect,however, that such containers cannot be readily packed in cartons, boxesand the like for shipment and storing purposes. In the case ofatruncated-conical as well as in case of truncated-pyramidalconfigurations, the narrow edge of the flange projects to all sidestogether with the cover connected thereto, and the actual containers arespaced relative to one another. In case no particular measures aretaken, for instance intermediately disposed cardboard strips or insertedcardboard panels, which center and retain the containers with apertures,containers packed in cartons or boxes can shift and damage each other,in particular under the effect of impacts during transportation.

In order to provide a remedy, containers have already been proposedwhich are formed substantially cylindrical or square and which have aflange throatlike constriction shortly below the flange receiving thecover disc, from the diameter of which constriction the flange extendsto the outer diameter of the substantial portion of the container.Containers formed in this way can be packed together in such a way thattheir side surfaces or the peripheral lines of their outer surfacescontact each other so that they are in a large-area contact, and in manycases particular measures can thereby be dispensed with when packing,since excessive area pressures which can result in a bursting of thecontainers are prevented by the large-area contact of the containersamong one another. Likewise, these containers are well-stackable by theupper taper. It has been found to be a disadvantage and broadly acceptedthat containers formedin this way require complicated equipment which issubject to operational trouble. In particular, the severing of theflange or the separating of the container from the plastic film materialserving as the forming material has proven to be difficult. Whensevering, comparatively high forces occur at shear pressures which aretransmitted to the two halves of the mold, for the mold must be dividedinto two because of the back-cut portions, so that it can be openedafter forming the molded article. For receiving these forces it isnecessary to also at least interlock the individual parts of the moldafter the aggregation thereof in order to be able to accept theseforces. Extreme attention must be directed to the guiding as well as tothe interlocking positions of the parts to be shifted laterally in orderto be able to maintain the small cutting gap closely defined. Inaddition to the presently existing difficulties of providing a two-pieceannular knife the further difficulties arise to impart the parts of theknife a precisely defined position for the next severing operationrespectively after shifting operations when opening the mold and touniformly accept the high forces occurring in the severing step. Sincethis can be approximated in practice only, the problem of high weararises in addition to the manufacturing difficulties and to thedifficulties inthe construction of the mold.

The invention provides an apparatus for such packaging containers havingbackcut portions which permits the cutting operations with a closedannular knife. This will simplify and render more economical themanufacture of the knife as well as the apparatus provided with theknife and will increase the life of the knife.

It is an object and a feature of this invention to solve this problem byopening the mold only within the region provided with the back-cutportions after the conventional preheating, prestretching and pneumaticexpansion into the desired shape and by moving at least one region ofthe mold non-interrupted on its circumference for a cut along the moldedarticle, i.e., in axial direction to a cutting plate.

The apparatus has proven to be well-suited which is formed only in theregion of the mold having the back out portions by separable mold partslaterally retractible, while at least one mold region non-tapered andnon-divided in ejecting direction ofthe molded article is provided, theface of which facing the cutting plate is provided with a cutting edge.

It has been found to bring about good results to provide the inner edgeof the non-divided mold region with the cutting edge. It has beenrecognized to be advantageous to release this cutting edge by anadditional axial retraction of the mold parts.

It has been found to be recommendable to press the front surface of thecutting plate against an abutment surface of the mold, in particular ofthe separable mold parts when the mold is closed. A particularlyeconomical manufacture can be accomplished with such an apparatus byproviding it with a plurality of molds in the form of a multiple mold.

With the foregoing object in view, together with such additional objectsand advantages as may subsequently appear, the invention resides in theparts, and in the construction, combination and arrangements of partsdisclosed, by way of example, in the following specification of certainmodes of execution of the invention; reference being had to theaccompanying drawings which form a part of said specification and inwhich drawings:

FIG. I is the illustration of an apparatus embodying features of thisinvention after forming the mold parts and after molding the filmmaterial into the molded article, and

FIG. 2 is an illustration of the apparatus of FIG. 1 after opening andlowering the separable mold parts as well as lifting the non-dividedmold region for the cutting step.

The apparatus of FIGS. l and 2 has a stationary bridge 1 which isprovided with a fluid cylinder 2 the piston rod 3 of which terminates ina prestretching punch 4. The knife 5 is carried by the punch 6 which inturn is connected to the bridge 1. and serves as a cutting plate. Thepunch has an axially shiftable depressor 7 at its outer lower end, saiddepressor being biased by means of spring means in direction; to themold against an abutment. I i

The apparatus furthermore has a platen 8 provided liftable and lowerableby means of a not illustrated drive, said platen being provided withguide members 10 adjustable in their height by fluid cylinders 9. Theguide members 10 contain fluid cylinders 11 by means of which the moldparts 12 are capable of being advanced for closing the mold toward thedie 13 and are capable of being retracted again for opening the mold.The die 13 is provided with an annular knife 14 at its upper innermargin. The mold bottom wall 15 closing the die at the bottom is forheight adjustment and is carried by the piston rod 16 ofa fluid cylinder17 which is connected to the base plate 18 of the apparatus. The pistonrod 16 is provided with a stop ring 19 which limits lowering movementsof the platen relative to the mold bottom wall; the limitation isselected in such a way that the mold bottom wall is capable of beingadvanced a little way beyond the face of the die 13 so that moldedarticles can be readily removed.

For forming a container first of all the mold is closed, i.e., the fluidcylinders 9 are extended together with the guide members 10, and thefluid cylinders 11 guide the two symmetrical mold parts 12 in directiontoward one another in such a way that their cylindrical regions engagethe outer periphery of the die 13 and encompass the mold cavity at bothsides in forming the mold throat, their free ends contacting each otherin the plane of symmetry of the mold extending normal to the drawingplane. Now plastic film material 20 preheated into the plasticized rangeis inserted and is retained by a further lifting of the platen 8together with the entire mold between the depressor 7 and the abutmentsurfaces of the mold parts 12 opposing it, the depressor being liftedfrom its abutment against the force of the spring biasing it. By afurther lifting of the platen under a defined pressure, the face of thepunch 6 can also be used for retaining or clamping the plastic filmmaterial 20, in case this is a requirement.

The actual molding operation is effected in the conventional way by twomethod steps: first of all the piston rod 3 is advanced together withthe prestretching punch 4 out of the position illustrated in FIG. 2 intothe position illustrated in FIG. 1, and the plastic film material 20 isthereby mechanically prestretched. By pressurizing the air supply duct21 ofthe punch 6 with compressed air, the plastic film material still inits plasticized condition is urged out of the prestretched positionagainst the walls of the mold and assumes the shape thereof. By coolingand when engaging the walls of the mold, respectively, the film materialloses its plasticity and results in the molded article 22 illustrated inFIG. 1 which is capable of being used as a container for variouspurposes. In the embodiment the container shape is substantiallycylindrical, and the upper rim is formed into a flange the outerdiameter of which corresponds to that of the cylindrical region of themolded article. Underneath the flange 23, the container is constrictedbottle-neck like. The shape of the container does not only cover acylindrical configuration, rather it can also be selected in any desiredshape.

For severing the flange or for separating the flange out of plastic filmmaterial or a plastic film web, first of all the mold parts 12 areretracted in order to release the constricted portion of the container.By an opposite pressurizing of the fluid cylinder 11 of the guidemembers 10 the mold parts 12 are retracted, and subsequently by anaccording pressurization of the fluid cylinders 9 the guide members 10are lower together with the mold parts 12 in relationship to the platen8 and the die 13 connected thereto, so that the face of the die islocated free. It has proven to be particularly satisfactory to lower theplaten 8 by a little degree prior to opening the upper molding region bylaterally moving apart the mold parts 12 in order to be able to open themold free of transversely acting forces. After the mold is opened, thecutting step can be performed. The mold bottom wall 15 is maintained inthe position it has assumed, and the platen 8 is lifted until thecutting knife 14 has its edges underneath the flange 23 underneath thedepressor. By a short further stroke the face of the depressor 7 isurged back beind the face of the punch 6, and upon passing of thecutting edges of the knife 5 and 14, the flange 23 is cut out of theplastic film material 20.

Subsequently the platen 8 is lowered to the limit ring 19 so that themolded article severed out of the plastic film material is freelypositioned on the mold bottom wall 15. After a slight lowering of themold bottom wall, the molded article 22 can be removed from theapparatus.

The apparatus of this invention has the distinctive advantage thatmolded articles can be formed having back-cut portions without it beingnecessary to divide the entire tool along a longitudinal plane and toopen it for removing the article. The stationary die at the same time isprovided for guiding and centering the separable mold parts 12 so thatparticularly precise and thus costly guide means can be dispensed with.Since the mold parts are only stressed with moderate forces and inparticular are not loaded by the high cutting pressure occurring duringthe cutting step, it is not necessary to provide particularly heavy-dutydrive and guide means. The face of the die 13 is released by thecomplete retraction and lowering of the mold parts 12, and it can beformed as a knife or be provided to receive a knife. Since the die 13and thus the knife 14 carried by it each are formed in one piece, it isnot necessary to make particular provisions for receiving the cuttingforces as a result of the stresses caused by the cutting step, like thiswould have been necessary when dividing the knife as well as the mold. Asimpleconstruction highly loadable apparatus is thereby obtained inwhich the centric guiding of the upper die edge serving as a movableknife can easily be accomplished. As a result of the good guidingeffect, however, the cutting gap can also be uniformly adjusted, and theadjustment is maintained over a long period of time so that a clean cutas well as low wear are always insured.

The apparatus used for the forming of containers can be furtherdeveloped. So for instance more than two mold parts can be providedwithin one region, and it is also possible to arrange separable moldparts in more than one region if more than one region having backcutportions for the predetermined molded article are intended. Theconstruction of the mold according to this invention can even be used,however, in case no punch cut is to be effected within the mold.Therefore it is possible to use the tool illustrated by way of examplein the figures for forming and separating molded articles, while asimilar tool is used for closing, i.e., for welding the moldedcontainers, which likewise comprises a die and two mold parts 12 as wellas possibly a mold bottom wall. The manufacture of such a tool can beperformed economical in particular for the reason that the same partsare used for the tool for molding and punching, as they are for thewelding station, and the drawings as well as the operations in theworkshop are identical for both tools.

Notwithstanding the illustrated uses of the invention and the manners bywhich such uses may be achieved, it is appreciated that changes andmodifications will suggest themselves to others skilled in the art bothfor uses similar to those illustrated as well as for other uses. Theinvention, therefore, is not to be deemed to be limited to the exactmodes of execution above disclosedby way of example, and it will beunderstood that the invention embraces all such changes andmodifications in the parts, and in the construction, combination andarrangement of parts as shall come within the purview of the appendedclaims.

I claim: 7

1. Apparatus for the production of containers with restricted throatportions, comprising in combination: die means having integral fixedvertical peripheral wall means with continuous peripheral knife meansformed at the upper edge thereof, a movable bottom wall inwardly of saidwall means to form a cavity for receiving sheet material therein to beformed into a container; mold element means at the top of said diemeans, said mold element means being radially movable inwardly andoutwardly relative to said die means, said mold element means being atits radially inward position inwardly of said continuous peripheralknife means forming a peripherally inwardly offset continuation of saidwall means when sheet material is being formed into a container, saidmold element means being moved to it radially outward position clear ofsaid continuous peripheral knife means and the vertical walls after thecontainer is formed; punch means positioned in registry with saidcontinuous peripheral knife means and engageable with the outwardlydirected periphery of the sheet material during forming of the containerand cooperable with said mold element means when in the inward positionto hold the sheet material in place during forming the container, andpressure forming means as sociated withsaid punch means for urging thesheet material into firm contact with said side wall means and bottomwall of said die means and into contact with said mold element meansthereby forming the container with a restricted throat portion; said diemeans with its continuous peripheral knife means being movable towardsaid punch means when said mold element means are moved to the outwardposition for cutting the outwardly directed periphery of the sheetmaterial and forming a flange on the formed container outwardly of therestricted throat portion after said container is formed, said bottomwall being movable relating to'said side wall means to allow thecontainer to be removed from the die means.

2. The apparatus for the production of containers according to claim 1,wherein said mold element means is formed of a two pieced split collararrangement which is moved in diametrically opposed directions to removethe mold element from between said punch means and said continuousperipheral knife means.

3. The apparatus for the production of containers according to claim 1,further including an annular axially shiftable depressor memberpositioned about said punch and in spaced alignment from said continuousperipheral knife means firmly to hold the outwardly directed peripheryof the plastic material being formed into a container between said diemeans and said punch means.

4. The apparatus for the production of containers according to claim 1,wherein said die means is supported on a movable platen, said platenbeing movable relative to the movable bottom wall of said die means,adjustable guide means secured to said movable platen and extendingupwardly therefrom for supporting said mold element means, and actuatormeanssecured to said adjustable guide members and connected to said moldelement means for actuation radially inwardly and outwardly for movementof said mold element means.

5. The apparatus for the production of containers according to claim 1,wherein said pressure forming means includes means adapted to be influid communication with a supply of air pressure, said air pressureassisting said forming means for ultimately urging the plastic materialin firm contact with the side and bottom walls of said die means.

1. Apparatus for the production of containers with restricted throatportions, comprising in combination: die means having integral fixedvertical peripheral wall means with continuous peripheral knife meansformed at the upper edge thereof, a movable bottom wall inwardly of saidwall means to form a cavity for receiving sheet material therein to beformed into a container; mold element means at the top of said diemeans, said mold element means being radially movable inwardly andoutwardly relative to said die means, said mold element means being atits radially inward position inwardly of said continuous peripheralknife means forming a peripherally inwardly offset continuation of saidwall means when sheet material is being formed into a container, saidmold element means being moved to it radially outward position clear ofsaid continuous peripheral knife means and the vertical walls after thecontainer is formed; punch means positioned in registry with saidcontinuous peripheral knife means and engageable with the outwardlydirected periphery of the sheet material during forming of the containerand cooperable with said mold element means when in the inward positionto hold the sheet material in place during forming the container, andpressure forming means associated with said punch means for urging thesheet material into firm contact with said side wall means and bottomwall of said die means and into contact with said mold element meansthereby forming the container with a restricted throat portion; said diemeans with its continuous peripheral knife means being movable towardsaid punch means when said mold element means are moved to the outwardposition for cutting the outwardly directed periphery of the sheetmaterial and forming a flange on the formed container outwardly of therestricted throat portion after said container is formed, said bottomwall being movable relating to said side wall means to allow thecontainer to be removed from the die means.
 2. The apparatus for theproduction of containers according to claim 1, wherein said mold elementmeans is formed of a two pieced split collar arrangement which is movedin diametrically opposed directions to remove the mold element frombetween said punch means and said continuous peripheral knife means. 3.The apparatus for the production of containers according to claim 1,further including an annular axially shiftable depressor memberpositioned about said punch and in spaced alignment from said continuousperipheral knife means firmly to hold the outwardly directed peripheryof the plastic material being formed into a container between said diemeans and said punch means.
 4. The apparatus for the production ofcontainers according to claim 1, wherein said die means is supported ona movable platen, said platen being movable relative to the movablebottom wall of said die means, adjustable guide means secured to saidmovable platen and extending upwardly therefrom for supporting said moldelement means, and actuator means secured to said adjustable guidemembers and connected to said mold element means for actuation radiallyinwardly and outwardly for movement of said mold element means.
 5. Theapparatus for the production of containers according to claim 1, whereinsaid pressure forming means includes means adapted to be in fluidcommunication with a supply of air pressure, said air pressure assistingsaid forming means for ultimately urging the plastic material in firmcontact with the side and bottom walls of said die means.